U.S. patent number 6,054,930 [Application Number 09/274,660] was granted by the patent office on 2000-04-25 for meter tamper detection device capable of counting multiple openings.
This patent grant is currently assigned to Schlumberger Industries, S.A.. Invention is credited to Jean-Louis Guillon.
United States Patent |
6,054,930 |
Guillon |
April 25, 2000 |
Meter tamper detection device capable of counting multiple
openings
Abstract
A device for detecting meter opening, the meter including at
least a first structural element and a second structural element
that are in a given position relative to each other when the meter
is closed, said device comprising: a moving member connected to the
first element and organized to take up a stable state or an
unstable state as a function of the displacement of one of the
structural elements relative to the other; holding means connected
at least to the second element and co-operating with the moving
member as a function of the displacement of one of the structural
elements relative to the other, so as to hold said moving member in
its unstable state and so as to enable it to go to its stable
state; and detection means suitable for determining the state of
the moving member and for emitting an opening signal when the
moving member is in a predetermined state.
Inventors: |
Guillon; Jean-Louis
(Migne-Auxances, FR) |
Assignee: |
Schlumberger Industries, S.A.
(Montrouge, FR)
|
Family
ID: |
9525034 |
Appl.
No.: |
09/274,660 |
Filed: |
March 23, 1999 |
Foreign Application Priority Data
Current U.S.
Class: |
340/637; 324/110;
361/667; 361/664; 340/666; 361/661; 340/542; 324/74; 340/870.09;
340/870.02; 340/545.6 |
Current CPC
Class: |
G08B
29/046 (20130101); G06M 3/12 (20130101); G01R
11/24 (20130101); G01F 15/007 (20130101) |
Current International
Class: |
G06M
3/00 (20060101); G01F 15/00 (20060101); G08B
29/04 (20060101); G01R 11/24 (20060101); G01R
11/00 (20060101); G06M 3/12 (20060101); G08B
29/00 (20060101); G08B 021/00 () |
Field of
Search: |
;340/545.6,666,542,637,870.09,870.02 ;361/661,664,667
;324/74,110 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Hofsass; Jeffery A.
Assistant Examiner: Nguyen; Tai Tan
Attorney, Agent or Firm: Pojunas; Leonard W.
Claims
I claim:
1. A device for detecting meter opening, the meter including at
least a first structural element and a second structural element
that are in a given position relative to each other when the meter
is closed, said device comprising:
a moving member connected to the first element and organized to
take up a stable state or an unstable state as a function of the
displacement of one of the structural elements relative to the
other;
holding means connected at least to the second element and
co-operating with the moving member as a function of the
displacement of one of the structural elements relative to the
other, so as to hold said moving member in its unstable state and
so as to enable it to go to its stable state;
detection means suitable for determining the state of the moving
member and for emitting an opening signal when the moving member is
in a predetermined state; and
control means connected to the detection means for causing the
moving member to return to one of its states, after an opening
signal has been emitted by the detection means when the moving
member has taken up the other state after one of the structural
elements has been displaced relative to the other.
2. A device according to claim 1, wherein the holding means
comprise a finger secured to the second element and co-operating
with a catch connected to the first element.
3. A device according to claim 2, wherein the catch is mounted on a
thin spring that bears against the finger when the meter is
closed.
4. A device according to claim 2, wherein the catch co-operates
with a main spring that is secured to the first element, said main
spring bearing against the finger when the meter is closed.
5. A device according to claim 1, wherein the detection means
comprise an electrical contact secured to the moving member,
another electrical contact, with the two electrical contacts
forming a switch, and a circuit for determining whether said switch
is open or closed.
6. A device according to claim 1, wherein the moving member is a
blade co-operating with return means suitable for returning said
blade to its stable position.
7. A device according to claim 1, wherein the moving member is a
piezoelectric blade.
8. A device according to claim 1, wherein the moving member is a
thermoelectric blade.
9. A meter including a device according to claim 1.
Description
The present invention relates to a device for detecting that a
meter has been opened, the meter including at least a first
structural element and a second structural element in a given
position relative to each other when the meter is closed. The
invention also relates to a meter provided with such a device.
BACKGROUND OF THE INVENTION
Meters, such as electricity meters, are entrusted to users who
might disassemble them in order to falsify them. That is why
operators and manufacturers of meters equip them with devices
making it possible to detect that a meter has been opened.
An old system consists in interconnecting the structural elements
of the meter that move apart when the meter is opened with an
authentication seal which breaks when the meter is opened. That
technique makes it possible to detect that a meter has been opened
only after the event, i.e. meter opening might be detected a long
time after the event, and, in addition, such detection requires a
human operator to intervene.
Document EP 0 490 710 describes another known technique for
automatically detecting displacement of the structural elements of
the meter on meter opening. The device described includes a
remanence magnetic circuit made up of at least two portions, the
position of one of the portions being dependent on the position of
the first element, and the position of the other portion being
dependent on the position of the second element, the magnetic
circuit thus being closed when said elements are in an initial
position, and being open when they are in any other position. The
device further includes means for exciting the magnetic circuit
while it is closed and in a determined magnetic state, and control
means connected to the excitation means for the purpose of
controlling said excitation means. Finally, that device includes
detection means suitable for producing a displacement detection
signal in response to a particular variation in the state of the
magnetic circuit under the effect of the excitation means, the
detection means advantageously including a single-pole detection
circuit.
By applying a suitable sequence of magnetizing/demagnetizing
operations to the magnetic circuit, that device makes it possible
to detect displacement of the structural elements of the meter
automatically, regardless of whether the displacement is temporary
or not, automatic detection being possible even after the event and
even if the device is temporarily deprived of electricity before,
during, or after meter opening.
That type of device is high in cost (compared with the overall cost
of the meter), even more so since the general trend in meter prices
is downward.
Document EP 549 519 describes another type of meter opening
detection device. A cam is connected to one of the screws of the
cover and it is rotated when the screw is unscrewed. The cam then
actuates a hammer which hits a piezoelectric plate. Under the
effect of the impact, the piezoelectric plate emits an electrical
pulse which is recorded in a memory.
Document FR 2 681 134 describes a device for opening the housing of
a meter, the device comprising a washer secured to a screw for
closing the cover onto the housing. A resistive track and a
conductive track for detecting the angular position of the washer
are provided. The angular position of the washer is stored, and a
microprocessor compares the current position of the washer with the
previously stored position. Any difference between the positions
indicates that the screw has been moved.
Document EP 447 615 describes various devices also using detection
of a change of position of a screw connecting the cover to the
housing to deduce whether the meter has been opened (or an attempt
has been made to open the meter).
OBJECTS AND SUMMARY OF THE INVENTION
The present invention provides a device for detecting meter
opening, the meter including at least a first structural element
and a second structural element that are in a given position
relative to each other when the meter is closed, which device is
low in cost (compared with the overall cost of the meter), while
retaining the possibilities of automatically detecting meter
opening even if the electrical power supply of the device is
interrupted.
For this purpose, a device of the invention comprises:
a moving member connected to the first element and organized to
take up a stable state or an unstable state as a function of the
displacement of one of the structural elements relative to the
other;
holding means connected at least to the second element and
co-operating with the moving member as a function of the
displacement of one of the structural elements relative to the
other, so as to hold said moving member in its unstable state and
so as to enable it to go to its stable state; and
detection means suitable for determining the state of the moving
member and for emitting an opening signal when the moving member is
in a predetermined state.
In a variant embodiment, the holding means comprise a finger
secured to the second element and co-operating with a catch
connected to the first element.
Advantageously, the catch is mounted on a thin spring that bears
against the finger when the meter is closed.
In another variant embodiment, the catch co-operates with a main
spring that is secured to the first element, said main spring
bearing against the finger when the meter is closed.
In a particular embodiment, the detection means comprise an
electrical contact secured to the moving member, another electrical
contact, with the two electrical contacts forming a switch, and a
circuit for determining whether said switch is open or closed.
The moving member may be a blade co-operating with return means
suitable for returning said blade to its stable position.
Alternatively, the moving member may be a piezoelectric blade, or
else a thermoelectric blade.
Preferably, the device of the invention further comprises control
means connected to the detection means for causing the moving
member to return to one of its states, after an opening signal has
been emitted by the detection means when the moving member has
taken up the other state after one of the structural elements has
been displaced relative to the other.
The present invention also relates to a meter including a device
having at least one of the characteristics presented above.
BRIEF DESCRIPTION OF THE DRAWINGS
Other characteristics and advantages of the invention appear
clearly from the following description given by way of non-limiting
example and with reference to the accompanying drawings, in
which:
FIG. 1 is an overall diagram of a first variant embodiment of a
device of the invention;
FIG. 2 is a diagram showing the FIG. 1 device on opening the
meter;
FIG. 3 is a diagram showing the FIG. 1 device on re-closing the
meter;
FIG. 4 is a diagram showing the FIG. 1 device after
re-initialization;
FIG. 5 is a diagram showing a second variant embodiment of a device
of the invention;
FIG. 6 is a fragmentary diagram showing another variant of a device
of the invention; and
FIG. 7 is a fragmentary diagram showing another variant embodiment
of a device of the invention.
MORE DETAILED DESCRIPTION
The device of the invention makes it possible to detect
displacement, from an initial relative position, of two structural
elements 1 and 2 of a meter 3 shown diagrammatically and in section
in FIG. 1.
For this purpose, in general, and as explained in more detail in
the description below, a mechanical memory having two states is
maintained in a first state under normal operating conditions, and
it is placed in a second state on meter opening. The second state
is maintained even after the meter has been re-closed, and until
meter opening has been detected and the mechanical memory has been
re-initialized, i.e. returned to its initial state.
For example, the meter 3 is an electricity meter, shown in
fragmentary manner, the element 1 being constituted by the housing
of the meter, and the element 2 being a terminal cover designed to
remain fixed to the housing under normal operating conditions. The
invention thus makes it possible to detect opening of the terminal
cover.
In the embodiment shown in FIG. 1, the device includes means 4, 5,
6 that are connected to the element 1 and that are part of the
two-state mechanical memory. These means include a moving member 4
which is suitable for pivoting about an axis perpendicular to the
plane of the figure, and which is fixed to a support 5. The moving
member 4, which is a plate or a blade in this example, is suitable
for pivoting between an unstable state, in which it is held in FIG.
1, and a stable state. The return means 6, constituted by a spring
in this example, exert a force urging the moving member 4 into its
stable position and holding it therein.
In FIG. 1, the meter is closed and operating normally. In which
case, holding means 7, 8, 9 connected to the second element 2
co-operate with the moving member 4 in a manner such as to hold it
in its unstable state. In the example shown, the holding means
comprise a catch 7 secured to a spring-forming thin blade 8 fixed
to the element 1 and having an end portion 8a in abutment against a
finger 9 fixed to the second element 2. The finger 9 passes through
the element 1 via an opening 10 provided for this purpose.
In this manner, the finger 9 holds the thin blade 8 in an extended
condition, and the catch 7 bears against the plate 4 so as to hold
it in the unstable position.
A description of how the device operates when the elements 1, 2 are
displaced relative to each other is given below with reference to
FIGS. 2, 3, and 4. Like reference numerals in the figures designate
like elements.
FIG. 2 shows that displacing the second element 2, and thus opening
the meter 3, causes the finger 9 to be withdrawn as indicated by
arrow 11, thereby releasing the end 8a of the thin blade 8. The
thin blade 8 thus takes up its rest position as indicated by arrow
12, entraining the catch which is secured to it. The withdrawal of
the catch 7 releases the moving member 4 which, under the effect of
the return force exerted by the spring 6, is returned to its stable
state, as indicated by arrow 13.
Opening the meter thus causes the moving member 4 to change over
from one state to the other. FIG. 3 diagrammatically shows the
effects of closing the meter 3, and thus of putting the element 2
back in place.
The finger 9 penetrating through the opening 10, as indicated by
arrow 14 comes into contact with the end 8a of the thin blade 8
which returns to its extension position, as indicated by arrow 15.
However, the moving member 4 which is in its stable state is not
re-engaged by the catch 7, and it retains its position.
Opening the meter 3, i.e. displacing the element 2 relative to its
initial position, causes the position of the moving member 4 to
change, whereas closing the meter 3, i.e. returning the element 2
to its initial position does not act on the position of the moving
member 4.
Opening the meter 3 can thus be detected automatically, merely by
detecting the change of state of the moving member 4, or, in
equivalent manner, by determining the state in which the moving
member 4 lies.
In the embodiment shown diagrammatically in FIGS. 1 to 4, means are
provided for determining the state of the moving member 4, and they
are constituted essentially by an electrical circuit that is closed
under normal operating conditions, and open when the element 2 has
been displaced. For this purpose, an electrical contact 16 is
secured to the moving member 4. Another electrical contact 17 is
provided so as to co-operate with the contact 16 to form a switch,
said switch being closed when the moving member 4 is held in its
unstable position and being open when the moving member 4 is in its
stable state.
The contacts 16 and 17 are connected to a microprocessor 18 which
tests periodically, e.g. every ten seconds, whether the switch
formed by the contacts 16 and 17 is open or closed. If the
microprocessor 18 detects that the switch is open, the moving
member 4 is therefore in the stable position, which means that the
meter 3 is open or has been opened.
The device operates even if the meter 3 is opened during an
interruption in the electrical power supply to the meter. The
moving member 4 changes over from one state to the other
independently of any electrical energy input. Once the power supply
is re-established, the microprocessor 18 automatically detects
opening of the meter 3.
In a variant embodiment (not shown), the means for determining the
state of the moving member may be optical means comprising a light
source emitting a light beam towards a detector. In one of its
states, the moving member interrupts propagation of the light beam,
while, in the other of its states, it allows the beam to propagate
freely. The microprocessor connected to the detector can thus
determine the state of the moving member as a function of the
signal emitted by the detector.
Once opening of the meter 3 has been detected, an opening signal is
produced by the microprocessor 18, which signal makes it possible,
for example, to increment a memory (not shown) in which successive
openings are counted. The opening signal may also trigger a warning
signal, cause a light-emitting diode (not shown) to be switched on,
or cause an opening message to be displayed on a display (not
shown) provided for this purpose.
Advantageously, the device of the invention includes control means
connected to the detection means for the purpose of causing the
moving member to return to its initial position, after an opening
signal has been emitted by the detection means.
As shown in FIG. 4, in this variant embodiment, the control means
comprise a coil 19 connected to the microprocessor 18. In this
case, the contact 17 is constituted by the end of a magnetic core
plunging into the coil 19. Triggered by the opening signal, the
microprocessor 18 emits an electrical pulse, e.g. having a duration
of a few hundredths of a second, sufficient to create a magnetic
field attracting the contact 16 and thus to return the moving
member 4 to its initial position as indicated by arrow 20.
The catch 7 is then positioned in a manner such as to hold the
moving member 4 in this position, even once the magnetic field has
disappeared.
The device is thus re-initialized and ready to detect any
subsequent opening of the meter 3.
FIG. 5 is a diagrammatic section view showing a variant embodiment
of a device of the invention. Unlike the preceding variant, opening
the meter causes the switch formed by the contacts 16 and 17 to
close.
This variant offers the advantage of removing any risk of poor
contact between the contacts 16, 17 under normal operating
conditions, which would lead to opening of the meter being detected
erroneously. Such poor contact can be caused by the catch not
pressing the moving member 4 properly against the contact 17.
In the embodiment shown in FIG. 5, the catch 30 is secured to the
coil 19. It is connected to a resilient blade 32 forming a return
spring suitable for urging the catch 30 to move parallel to the
plane of the figure. FIG. 5 shows the device under normal operating
conditions, the blade 32 being in the rest position.
Under normal operating conditions, the catch 30 holds the moving
member in its unstable state, only the contact 16 of the moving
member being shown.
Displacing the finger 9 releases a spring-forming thin blade 34
which bears against the end 30a of the catch 30, thereby causing it
to be withdrawn in translation, thereby releasing the contact
16.
The second contact 17 which co-operates with the contact 16 to form
the switch is placed facing said contact 16 so that, when the catch
30 releases the moving member, the return means provided for this
purpose but not shown in FIG. 5 press the contact 16 against the
contact 17. The return means may, for example, be constituted by a
spring as in the preceding variant.
The detection means which are, for example, identical to those
described above (not shown) periodically test the state of the
switch formed by the contacts 16 and 17, the closed state
indicating meter opening. In which case, an opening signal is then
emitted that has the same effects as those described above.
The embodiments shown in FIGS. 1 to 4 and 5 offer the advantage of
being suitable for implementation using simple components such as
relays which include the contacts necessary to form the switch, and
return means, and they enable the device to be re-initialized by
means of an electrical pulse.
Various other variants are possible for the device of the
invention. For example, the return means 6 may be constituted by
the moving member 4 being mounted resiliently on the support 5.
In another variant embodiment shown in fragmentary manner in FIG.
6, the moving member 4 may be constituted by a piezoelectric thin
blade enabling it to be returned to an unstable position and
participating in the control means by replacing the coil 19. In
equivalent manner, the thin blade may be made of a thermoelectric
material. In which case, a winding placed around the blade makes it
possible for it to be heated under the effect of an electrical
pulse, thereby deforming it and causing it to go from one state to
the other.
FIG. 7 is a diagrammatic fragmentary view showing another variant
embodiment of the device of the invention. A contact 16 is disposed
on the moving member 4, which, in this example, is a spring-forming
thin blade. The contact 17 secured to the element is placed facing
the contact 16 so as to form a switch which is closed when the
blade is held in the unstable position by the catch 17, and which
is open otherwise.
Once the element 2 (not shown) has been displaced, the catch 7
releases the blade 4, thereby opening the switch. Once opening has
been detected, once the number of openings has been incremented,
and optionally once warning signals have been emitted, the control
means re-initialize the device, the microprocessor (not shown in
FIG. 7) transmits a suitable electrical signal to a coil 36 so that
the plunger core 38 is displaced in the direction indicated by
arrow 40 so as to return the moving member 4 to its unstable
state.
Regardless of which variant is chosen, the device of the invention
makes it possible to detect opening of a meter automatically, even
if the electrical power supply to the device is momentarily
interrupted, and to do so at low cost. In addition, such a device
may be implemented with elements easily adapted from commercially
available components.
* * * * *